Alkali metal process



2 sneets4sheet 1 Filed Aug. 13, 1929 June 6, l- F` WAlT 1,913,145

ALKALI METAL PROCES S AFiled Aug. 13, 1929 2 Sheets-Sheet -2 M npemtoz @51, Vv @um gif/Www Patented June 6, 1933 UNITED STATES JUSTIN F. WAIT, or NEW YORK, N. Y.

'ALKALI METAL PROCESS Application le. VAugust 13, 1929. Seria1 No. 385,597.

This invention relates chiefly to methods of preparation of alkali metals or solutions of these metals and their compounds in compounds of alkali metals, and the use of such compounds and solutions in fusions as in the manufacture of organic chemicals. I have found that by using the methods described herein that it is possible to greatly reduce operating hazards and to lovver cost of manufacture of alkali metals and compounds thereof, and to decrease the cost of production of organic chemicals Whose manufacture involves the use thereof.

In many chemical processes, mixtures of compounds of alkali metals are used and it is desirable to alter the proportion of the metals involved. y Again, in mixtures of the hydroxides of the alkali metals it is often desirable to decrease the hydroxide content. This is done by subjecting the concentrated or fused compounds thereof to electrolysis thus depositing one of the metals, such as breaking sodium hydroxide into its parts and producing metallic sodium, and at times the further conversionof sodium into sodamide by the action of ammonia.

By the term fused is meant that'state existing when a solid compound is heated to the point where its properties approach those of a liquid, this point usually being near the melting point of the compound involved.

The effect of moisture a`nd other` foreign products -is to alter the fusion point so that it does not equal the true melting point of the pure compound. As a salt or hydroxide containing W'ater is concentrated as by evaporation, it gradually approaches the condition of dehydration which term is applied in the art to the condition of being approximately Water free in the sense that most of the water has been removed, as compared with the state of absolute dehydration wherein all of the Water has been removed except traces or Water which may bein definite chemical or physical equilibrium With the conditions involved.

The process may be used to produce a state of" dehydration of compounds of alkali metals, wherein the Water content is decreased or. entirely removed by electric power. Relatively cheap electricity isthus substituted for more expensive chemical heating or other means as has been used in the past. As an example 'of this, the moisture content of a con-nnercially and partially dehydrated hydroxide of sodium may be removed by electrolysis of the fused mass thus producing a state of complete dehydration. Furthermore, vacuum may be applied to the operation, to assist in carrying off gaseous pro'd- 60 ucts of the electrolysis producing the metal. In case Where an excess of a dehydrating agent is required, the electrolysis may be continued past the dehydration point, thus creating an excess of free sodium. In operating' a cell continuously for this purpose it is therefore but necessary to discharge both fused hydroxide and metal as contrasted With the usual method of operation whereby sodium alone is 'discharged in one system, 70 the isolated metal being later added to the hydroxide.

As an alternate method of dehydrating the fused material, it is economical to add to the partially dehydrated compound,a mixture or solution of the compound containing free metal or some derivative thereof as, for example, a solution of sodium or sodamide in fused caustic soda. This method eliminates some of the corrosive and hazardous conditions involved in electrolysis of such compounds when mixed With small amounts of Water.

In using alkali metals for the preparation or treatment of chemicals it has been the usual practice to isolate the metal, solidify the same, pack, `store and shipthe same. Thereafter the metal would again be made fluid and used. This has involved unusual hazards affecting both life and health and has cause a loss in yield due in part to handling and exposure to the elements'.v

My invention involves the use of a closed system which greatly reduces the hazard and prevents air and other elements from acting in a deleteriousmanner. It results in less' costs of labor, yield and insurance and greatly improves the safety and the health of the operators.

of the alkali metal or its derivative such as its amide, in relativel dilute solution in a gives excellent results in organic synthesis.

Careful control of the temperature of reaction is essential to obtain good energy and current efficiencies and to obtain maximum capacity for a cell unit. As a very'satisfactory method for obtaining this control and to abstract relatively large I have adopted or added ing to electrolysis which a method of heatpreferably involves olling mercury or alloys thereof, and reduces mechanical difficulties previously experienced.

In the electrolysis of fused hydroxides, passage of a gas through the mass assists in removing the products of the reaction and if an amide of the metal is desired, ammoniagas is passed into the mix thus converting the metal directly into the amide. In fusing a mixture of sodium hydroxide for example, it is possible to lobtain a solution of sodamide in alkali directly bythis method. This solution may then be `used as for dehydration of a dyestufl" intermediate and for removing water from fused compounds which are partially dehydrated.

Fusions carried out in mixtures of compounds of alkali metals have the advantage of greater fluidity of mix and make it possible to operate at a temperature below the melting point of a single compound. v Such fusions are sometimes carried out with the use of a dehydrating agent as an alkali metal or a compound thereof. On the recovery of the hydroxides therefrom, it is desirable to readjust the ratio of the component parts which may be done by electrolysis. If for example, sodamide is used as a dehydrating agent in a mixture of sodium and potassium hydroxides, the sodamide is decomposed into sodium hydroxide as it reacts, thus altering the ratio of sodium and potassium h droxides. The caustic mixture may then lie recovered and readjusted to its original state by electrolysis, yielding the free metal which may then be converted into the amide by the action of ammonia. In some prior processes it has been customary to remove the excess sodium that was formed during the reaction by pure chemical means as by conversion into carbonate and mechanically separating it. This required subsequent readjustment and dehydration as for example by the addition of caustic potash and sodamide.

An improved method for the manufacture of sodamide from sodium, in preparation for quantities of heat'..

its addition to fused alkali to form a fusion mixture, is covered by my Patent No. 1,646,375. This process is expensive and dangerous as compared with the above process involving the cycle indicated. When a solution of sodamide in alkali hydroxides is desired, economical operation may be had by preparing a solution of sodium in hydroxide and treating the mixture with ammonia. By proper operation of special apparatus theltwo steps may be carried out simultaneous y.

In the operation of the ordinary electrolytic cell such as has been used' for the treatment of an alkali metal, the material has been charged into the cell in approximately the exact amount required for decomposition. In most instances, the flow of the products has been in a different direction from the natural flow of the material through the cell. I have found numerous advantages in causing a parallel flow of the products of decomposition and the compound charged in excess of that used in decom osition. This includes reduction in the diflhsion which is detrimental to high yield and elliciency. It is also possible to so control the feed and the electrolysis as to yield a final product containing the desired percentage of alkali metal or its derivative.

The lowering of the melting point as by use of'a mixture of two alkali compounds renders the system more positive and' less hazardous. The increased fluidity also makes it ossible to operate at lower temperatures t an is .otherwise possible. In the electrolysis of mixtures of compounds of two metals it is sometimes possible to set free two metals in a proportion depending upon their natural properties and the controlled conditions including current, temperature and velocity.

After the fusion has been completed, the organic salt may in some cases be recovered by concentration or nearly complete separation from the alkali compound by filtering. If a fluid' material such as a mineral oil is added it may facilitate'this separation. In this case the alkali compound or part thereof may be recovered and received without such alarge expense of diluting as is ordinarily resorted to. Y

This description and the exam les mentioned above show some of the possible applications of my invention, but I do not limit my claims to the exact d'etails described herein. The following is given as a particular illustration of an arrangement of apparatus for carrying out the invention.

In the drawings Fig. 1 is a vertical section through a cell and Fig. 2 is a somewhat diagrammatic arrangement of apparatus that may be used in carrying out the invention.

The electrolytic cell shown in Fig. 1 consists of a container 1 with an inlet 2 for a fused alkali compound, such as sodium hydroxide for example, and an outlet 3 so ad-v justed as to maintain the desired liquid level. The fused material is passed in any convenient way through the electrolysis-zone 4 which vmay be annular in shape. The electrodes 5 and 6 are connected to a source of direct current thus causing flow of electricity radially across the zone 4 whereby electrolysis takes place, the alkali metal being released at the surface of the electrode 5. i f

A line gauze 7 is placed so as to prevent diffusion of deposited molecular substances includingthe alkali metal. This gauze is preferably hung from a support 8 lca-rried by the cover plate 9. An opening 10 may be provided in the cover 9 for inspection and to release gases. A removable cover may be provided, if desired, to close the opening 10.

Gases liberated at the surface of the electrode 6 may be collected in an annular chamber 11 and vented through the outlet 12. Gases liberated at the electrode 5 may be collected in the dome 13 and vented through the outlet 14. The cover plate 15 is removable and may be used to Carr a gas inlet 16 connecting a gas distributmg ring 17 vhaving outlets 18. The ring 17 or its equivalent may be located at or below the annular electrolysis zone 4.` The chamber 19 may be provided for a. temperature control substance, such as mercury. Vapors may be introduced through the pipe 20 and condensate drawn off through the pipe v21. When cooling is required, a con- -nection to pipe 21 may be provided to maintain a liquid mass in the chamber 19, the piping being such that the exothe'rmic heat may be absorbed by causing the liquid in the chamber 19 to boil, the vapors passing to condensers connected to the pipe 20.

One side of a source of direct current is connected to the pipe 22 which is connected to the electrode 5 and insulated from the opposite side by the insulating material 23. The other side of the electric current line is connected to the container 1 and is thus connected to the electrode 6. The current passes through the zone 4 acting upon the fused alllrali compound that is passing through the ce l.

The de osited metal accumulating at the surface o the electrode 5 passes upwardly in the current of the fused compound. Should its deposition exceed the solubility, the metalr lic substance would rise more rapidly if and when its densit is less than that of the alkali compound. il low the dome 13the alkali metal, if sodium, may be acted' upon by the gas which, if ammonia, produces sodamide. The resulting solution of sodamide in the sodium hydroxide may be controlled to yield for example a 14% solution which is suitable for chem'ical reactions such as the production of indigo by the fusion and dehydration of a salt of phenylglyeine.

The entire process may be carried out as pon entering the region be-v indicated in Fig. 2, the cell 1 being made as described above in connection with Fig. 1. The fusing of the organic salt, such as phenylglycine for example, is carried out in the fusion pot 24 the gaseous amonia efiiuent being carried off through the outlet 25 as the reaction, aided by agitation, progresses. The organic salt may be charged gradually through a mechanical feed hopper 27, the iinished fused mass being discharged through the outlet 28 into the dilution tank 29 previously charged with recovered or fresh water through the pipe 30. lf air or ozone oxidation is used to precipitate the indigo in the tank 29 it may be introduced through the pipe 31 and bubbled through the liquid mass. The use of a cooling means, such as a ilaker for example between the fusion pot 24 and the dilution tank 29 sometimes results in higher chemical yields.

The indigo may be withdrawn from the tank 29 through the outlet 32 and concentratedand separated from the dilute caustic by countercurrent flow through thickeners V33 and 34 in series and the continuous filter 35. The thickened slurry from the thickener 33 is preferably mixed with Water in the agitation chamber 37. The liquid from the thickener 34 contains some caustic and is used in the dilution tank 29, that from the thickener 33 is evaporated in the evaporator 36 which may be single stage or multi-stage. It is provided with steam connections 37 and a vacuum connection 38. The indigo delivered by the filter 35 Will be of suitable composition for drying or standardizing as a paste.

' The concentrated caustic from the evaporator 36 will pass through its outlet 39 and into a heated dehydrator 40 wherein the caustic liquor of 45-55% strength may be concentrated to a moisture content of about 0.3%. Thereafter the caustic is preferably passed from the dehydrator 40 into a storage tank 41 which may also function as a secondary dehydrator, this tank acting as such when it receives sodamide-caustic solution from the cell 1. The fused caustic then containing only traces of water may be charged 'through the inlet 2 into the cell 1, where it is electrolyzed and reacted upon thus completing the cycle.

Ammonia gases liberated from the cell 1, the fusion pot 24 and the dehydrator 41 may be recovered by collection in the absorption towers .42 and .43. The towers 42 and 43 are provided with Water connections 44 and 45. The gaseous ammonia is regenerated in the ammonia generator 46 that is provided with steam connection 47 and water connection 48. Evolved hydrogen gas is vented from 49. Cooling coil connections 50 are preferably connected with cold brine or the ammonia system may be used as shown in my Patent No. 1,452,009.

For the manufacture of indigo a mixture of approximately equalparts of sodium and potassium hydroxides have been found to be quite satisfactory for fusion purposes. Its relatively low melting polnt 1s also of assistance in flowing the mass through .the system and in controlling the cell operation. I claim; 1. The process of producing an alkali metal which comprises passing a fused alkali metal hydroxide through an electrolytlc z one at a rate in excess of the rate of electrolysis and in a manner to deliver beyond the zonex a mixture of the metal and the hydroxide.

2. The process of electrolyzing a hydroxide of lan alkali metal which comprises passing the hydroxide through an electrolysis zone, causing continuous movement of the hydroxide and removing the unchanged pormoisture content, and releasing free metal by passage of the so treated hydroxide through a defined electrolytic zone at a rate in excess of the decomposltlon.

JUSTIN F. WAIT.

tion of the hydroxide-in the direction of the fiow of the products ofvelectrolysis.

3. The process for the manufacture of an alkali metal which comprises flowin a fused hydroxide thereof through a defined electrolytic zone subjected to current How under controlled electrical potential suicient to release free metal, and controlling the velocity of said hydroxide at a selected speed of passage upwardly through said zone, said speed, being in. excess of the rate of electrolytic decomposition of said hydroxide and discharging the metal so released and a quantity of hydroxide approximately equivalent to that excess.

4. The process for the manufacture of an alkali metal which comprises electrolyzing a completely fused hydroxide thereof by pas 'sage thereof at controlled velocity upwardly through a defined'zone of electrolysis at a rate in excess of the rate of decomposition of said hydroxide into free and dlscharging a quantity ofthe hydroxide approximately equivalent to that excess.

5. The process for the manufacture of an alkali metal which comprises electrolyzing a fused hydroxide thereof in a confined electrolysis zone by passin said hydroxide in controlled upward veloclty through said zone and feeding into the electrolysis zone an excess of the hydroxide above that converted into the metal, and discharging a quantity of the hydroxide approximately equivalent to that excess. l

6. Thev process of producing and treating an alkali metal which comprises passing a fused alkali metal hydroxide through a defined electrolytic zone at a rate in excess of the rate of electrolysis and in a manner to `deliver beyond the zone a mixture of the metal and the hydroxide and reacting soreleased metal with ammonia at about the time of release of said metal.

7. The process of producing an alkali metal which comprises treating fused 'commercial alkali hydroxide with a dehydrating substance,lelininating substantially all of its metaLbyelectrolysis l 

